CD4 and infection: The role of multifunctional CD8+ T-cells and their associated signatures related to the lethal and nonlethal models of O. tsutsugamushi infections were less numerous; moreover, the overall numbers of CD8+ T-cells that were elicited in both the lethal and nonlethal models of infection were reduced in comparison to the CD4+ T-cell populations (Figure 4 and Figure 5).